android - How can I specify the type of the field that an Annotation should be applied to in Java? -


i'm creating simple annotation, me inflating settings inside android application. annotation this:

@target(elementtype.field) @retention(retentionpolicy.runtime) public @interface coresettings {     string name() default ""; }

i want ensure used in fields type extends custom class named basesettings. in example below, mainsettings extends abstract class basesettings.

public class mainactivity extends baseactivity {      @coresettings("prefs")     mainsettings settings;       (...)  }

how can it?

yes, can cause compiler issue error message if write annotation on field of wrong type.

you cannot using @target meta-annotation. in addition, need write annotation processor. annotation processor examine each occurrence of annotation @coresettings in source code, , issues error (just other compiler error) if @coresettings applied type not extend basesettings. short, simple annotation processor write.

you compile-time warning when running annotation processor, can add -processor ... command-line argument javac in project's buildfile.


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